my exact thinking.
for my evasion based ranger pathfinder burning arrow in hardcore legacy this might just save my life. its bonkers to run eva bssed builds anyway. but balls in or no balls...
I run fire as my lowest resist to benefit from the obvious death threat from reflected fire damage.
also another nice way to mitigate would be to combine it with a lightning coil and low lightning cap. thus u would further reduce the physical damage taken as lightning.

The most important question: does this flask snapshotting my resists on use? F.e. I have all 3 uncapped resists 135%. Now i'm using The Wise Oak and getting 10% reduction of each element and 20% penetration for each element. And right after that (next second) i'm pressing Vessel of Vinktar Topaz Flask. I still have that bounus from The Wise Oak or it's recalculated and now i have only 20% penetration for lighting and 10% reduction to cold and fire?

Just wanted to poke my nose in and offer kudos to ToBeSomebody. I always like seeing uniques like this, with interesting buildy properties that encourages at least a modicum of thought, as opposed to 'ball-O-crezze-stats' stuff like Skyforth. As one of those brainless buffoons who doesn't turn every build in the game into CI/GR/VP triple-dipping turbo cheese, I can state that Wise Oak is on my list of interesting tools and I'm looking forward to eventually snagging one and trying it out.

The most important question: does this flask snapshotting my resists on use?

Considering GGG has been working hard to remove every instance of snapshotting, and various other buffs and debuffs can retroactively change stats, it's a very safe bet to say the Wise Oak does not allow snapshotting.

The flask effects change as your resists do, even after changing gear or using an ele res flask. If you activate it with higher fire res, then use a topaz flask. You'll lose the fire pen and instead gain lightning pen.

Just looking at the mechanics, the defining aspect of this Flask to me is that it stacks with existing elemental mitigation options. That 14.3% more EHP I mentioned earlier works on top of +x% to maximum Elemental Resistances and has additional synergy with other Reduced Damage Taken modifiers. When I look at this flask I see an elegant solution to Volatile Eleblood for Life-based Melee builds, though I'm not sure the exact numbers work out to always prevent one-shots - probably not, for Guardian/Shaper Maps with 5 damage mods, but I don't know if even the vaunted CI/VP/GR meta can handle those with no risk of RIP.

What does this mean if I have 84 elemental resistances and 50% increased flask effect?

Would I take 16% of initial hit and then that amount is reduced by 15% or 13.6% of the initial hit instead? so in this case it acted as 2.4% additional max resist so I effectively have 86.4% max resist?

Would I take 16% of initial hit and then that amount is reduced by 15% or 13.6% of the initial hit instead? so in this case it acted as 2.4% additional max resist so I effectively have 86.4% max resist?

Sure, assuming flask effectiveness works on the unique mods, if that is literally your only source of reduced elemental damage taken. The amount would be reduced by 35% instead of 15% with a vanilla Fortify, and more with increased Fortify effectiveness or other applicable RDTs, especially from Ascendancy. (Jugger full charges, Champion's taunt travel node, Gladiator's bleeding terminal node, Saboteur's blind terminal node, Elementalist's anti-reflect stubble, Trickster's mana stubble, and probably a few others I'm missing).

Although I guess if you prefer to think purely in terms of increased maximum resistance, you could just take the other RDTs as +x% max resist there, too, and think of Wise Oak as "forever 2.4%." If you did that, you would hopefully keep in mind how +maximum resistance has increasing returns asymptotically towards infinity (y'know, like how at 98% current, +1% max res is the same as 50% Less Damage Taken, or 100% more EHP).

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